The present invention relates to a process of and an apparatus for packaging an article in a receptacle to obtain a vacuum pack.
Hitherto it has been known to package an article in a plastics envelope, such as a plastic bag, by loading the article in the envelope and then inserting the loaded envelope into a vacuum chamber for the atmosphere around the envelope to be reduced in pressure so that the air or other gas within the envelope is extracted and finally the envelope can be sealed under low pressure conditions. The resulting package is termed a "vacuum package".
It is also known for the operation of the process to be such that during the reduction in pressure of the atmosphere around the envelope, the wall of the envelope baloons away from the enclosed article, so that the extraction of air from within the envelope can be more effectively carried out. Such a system has, for example, been disclosed in U.S. Pat. No. 3,714,754 (Holcombe) using a nozzle to extract air from within the envelope while the pressure of the atmosphere around the envelope has reduced to effect the necessary ballooning action. Ballooning has furthermore been disclosed in U.S. Pat. No. 3,832,824 (Burrell) in which the vacuum chamber in which the envelope is closed has two portions of which a first portion encloses the envelope mouth and the second portion encloses the article-enclosing remainder of the envelope so that the pressure around the exterior of the envelope can initially be reduced more rapidly than the pressure within the envelope (in order to promote the desired ballooning effect). Such a process is suitable for a high vacuum pack when a long evacuation step can be tolerated. Furthermore, sealing the pack while it is in a ballooned condition will give rise to uncertainty of the volume of residual air still in the pack at the time of sealing, leading to uncertainty of the air pressure within the sealed bag when the pack exterior is returned to atmospheric pressure outside the chamber.
When using such process for packing products having a porous structure the high vacuum applied can remove air out of the product so that the structure of the product will be destroyed or at least damaged.